Electrical coil structure for inductive apparatus



Feb. 16, 1965 B. J. PALMER 3,170,134

ELECTRICAL COIL STR UUUUUUUUUUUUUUUUUUUUUUUUU US Fi l e d D e c 1 5 l 961 Feb. 16, 1965 a. J. PALMER 3,170,134

ELECTRICAL con. STRUCTURE FOR mnucnvs APPARATUS FilGd D60. 15, 1961 4Sheets-Sheet 2 Fig. 2.

Feb. 16, 1965 B. J. PALMER 3,170,134

ELECTRICAL COIL STRUCTURE FOR INDUCTIVE APPARATUS Filed Dec. 15, 1961 4Sheets-Sheet 3 Fig.3.

Feb. 16, 1965 a. J PALMER 3,170,134

ELECTRICAL COIL. STRUCTURE FOR INDUCTIVE APPARATUS Filed Dec. 15, 1961 4Sheets-Sheet 4 N N 92 N N N I i u i United States Patent Ofiice3,170,134 Patented Feb. 16, 1965 3,170,134 ELECTRICAL COIL STRUCTURE FORINDUCTIVE APPARATUS Betty J. Palmer, Sharon, Pa., assignor toWestinghouse Electric Corporation, East Pittsburgh, Pa., 21 corporationof Pennsylvania Filed Dec. 15, 1961, Ser. No. 159,699 Claims. (Cl.336-205) This invention relates in general to electrical inductiveapparatus and more particularly to coils for inductive apparatus such astransformers.

Transformers of the prior art have conventionally used a coil wound on aform made from multiple turns of an insulating paper having a coating ofan adhesive on one or both sides of the paper. The process of depositingthe adhesive on the insulating paper increases the cost of the coilinsulation and, of course, increases the cost of the apparatus.

Accordingly, it is a general object of this invention to provide animproved electrical inductive apparatus, such as a transformer.

It is a more particular object of this invention to provide a new andimproved inexpensive coil for electrical inductive apparatus, such astransformers.

Briefly, the present invention accomplishes the above cited objects byproviding a coil form wound from an uncoated, thermally stabilizedinsulating paper. The conductor used to wind the coil may be round orrectangular wire or foil or sheet conductor material. A liquid adhesiveis poured into the coil at spaced intervals so that it flows between theseveral layers of insulation and conductor. The coil is then heated inan oven to cure the adhesive. The liquid adhesive may be eitherthermosetting or thermoplastic provided it has a sufiiciently highmelting point to remain solid at the operating temperature of theapparatus.

Further objects and advantages of the invention will become apparent asthe following description proceeds and features of novelty whichcharacterize the invention will be pointed out in particularity in theclaims annexed to and forming a part of the specification.

For a better understanding of the invention, reference may be had to theaccompanying drawings, in which:

FIGURE 1 is a top view of a transformer coil made in accordance with myinvention;

FIG. 2 is a sectional view of another transformer coil made inaccordance with my invention;

FIG. 3 is a sectional view taken along the line III-III of FIG. 1; and

FIG. 4 is a sectional view of a modified embodiment of my invention.

The coil illustrated in FIG. 1 is formed by winding a strip of thermallystabilized insulating paper on a mandrel to form an insulating coil form10. A first section 12 of low voltage winding is wound on the coil formIt The low voltage winding is a plurality of turns of copper or aluminumfoil or sheet conductor. The foil or sheet conductor used to wind thelow voltage winding may be insulated prior to winding, for example, bycoating it with an insulating enamel. To further insulate one layer ofthe winding from an adjacent layer of the winding a strip 14 ofinsulating material, such as thermally stabilized insulating paper, iswound between each layer or turn of the foil or sheet conductor. Thenumber of turns of the insulated foil or sheet conductor comprising thelow voltage winding 12 is, of course, determined by the transformervoltage and current rating desired.

The next layer 16 is thermally stabilized insulating paper wound on topof the last turn of the low voltage winding 12.

A corrugated fibrous strip of material, or a plurality of pressboard orwood strips 18 placed at the ends of the transformer provide a duct 20for the circulation of a liquid dielectric adjacent to the end turns ofthe low voltage winding 12. The wood or other insulating strips 18 areglued to the last turn of the insulating tube 16 around the ends of thetransformer to provide a space or duct 20 adjacent to the tube 16. Thisspace or duct 26 allows the liquid dielectric to circulate between thelow voltage winding 12 and an insulating tube 24.

The insulating tube 24 is formed by winding on top of the tube 16 asmany layers of insulating paper as required to insulate the low voltagewinding 12 from the high voltage winding. The first or inside section 22of the high voltage winding is comprised of a plurality of layers ofsheet or foil conductor wound on the tube 24 with a turn of thermallystabilized insulating paper between each layer of the conductor.

A strip of corrugated fibrous sheet or a plurality of pressboard or woodstrips 26 is placed at the ends of the transformer on the first section22 of high voltage winding. The corrugated strip 26 provides a pluralityof ducts 28 for the circulation of the liquid dielectric between thesections 22 and 30 of the high voltage winding.

The second section 30 of high voltage winding is Wound in the samemanner as the first section 22. That is, alternate layers of conductorand insulating paper are wound on the first section 22 of the highvoltage winding with the corrugated fibrous strip 26 therebetween at theends of the transformer. As many sections of high voltage winding wouldbe used as are required for proper cooling of the winding at thetransformer rating desired.

On the last section 32 of high voltage winding another duct 34 isprovided, for example, by wood strips 36 affixed thereto, for thecirculation of the liquid dielectric adjacent to the last section 32 ofthe high voltage winding.

Another insulating tube 38 wound, on the last section 32 of the highvoltage winding, using thermally stabilized insulating paper providesthe necessary insulation between the outside or last section 32 of thehigh voltage winding and the inside layer 40 of an outside section ofthe low voltage winding. The outside section of the low voltage windinglike the inside section is comprised of two layers 49 and 42 of enamelinsulated wire or foil electrical conductor with a layer 44 of thermallystabilized insulating paper between the layers 40 and 42 of the lowvoltage winding.

The final layer 46 of material on the coil is a turn of thermallystabilized insulating paper wound on the outside layer 42 of the outsidesection of the low voltage winding.

After the entire transformer coil is wound a liquid adhesive, such as anepoxy resin, is poured into the transformer at spaced intervals, forexample, the areas 48, 50, 52 and 54 at the four corners, so that itwill flow in an axial direction between the multiple layers of theinsulation and conductor. The coating of adhesive may extend from oneface of the coil completely through the coil, in an axial direction, tothe opposite face of the coil. However, when foil or sheet conductor isused only the edges of the foil need to be coated with the adhesive.Coils with adhesive on only the top and bottom, 0.5 inch of foil, weretested and withstood a full short circuit without damage due tomovement. The transformer is then heated to a temperature of C. to C.which cures the adhesive poured between the layers of the transformerthereby firmly bonding the plurality of layers of insulation andconductor together to provide a solid coherent unit and prevent axialshifting of the electrical conductors upon short circuiting of thewindings of the coil.

A transformer coil having only one section of low transformer coil.

voltage winding and one section of high voltage winding is illustratedin the sectional view of FIG. 2.

Like the transformer coil of FIG. 1, a strip of insulating paper iswound on a mandrel to form a tubular coil form 60. A plurality of turnsof metallic foil or sheet electrical conductor is then wound on the coilform 69 to form a first or inside section 62 of low voltage winding. Thefoil or sheet used to wind the coil is coated with a material such asenamel to provide coil turn-to-turn insulation. A strip of thermallystabilized paper is wound over the first section 62 of low voltagewinding to form a tubular insulating member 64 between the sections 62and 66 of the low voltage winding. The second section 66 of low voltagewinding is, like the first section 62, a strip of enameled sheet or foilconductor wound on the insulating member 64 to form a plurality of turnsof the low voltage winding.

Another insulating member 68 is wound from a strip of thermallystabilized paper to provide insulation for the low voltage winding. Aduct '70 is then formed at the ends of the coil by a corrugated fibrousstrip, or a plurality of pressboard or wood strips 71.

The next layer 72 is another insulating member wound on the member 68and the duct forming members from the thermally stabilized insulatingpaper. The num er of turns of paper used to form the member 72 is, ofcourse, determined by the voltage difference between the low voltagewinding and the high voltage winding.

The high voltage winding 74 is, like the low voltage winding, Wound froman insulated sheet or foil conductor with a strip of insulating paperbetween layers of the winding to provide layer-to-layer insulation. Thefinal layer 76 on the single section transformer coil of FIG. 2 is aplurality of turns of thermally stabilized insulating paper. The numberof turns is determined by the voltage at whichthe high voltage windingis operated.

A liquid adhesive, for example an epoxy resin, is poured into thecompletely wound coil at spaced intervals so it will flow between theseveral turns of insulating paper and sheet or foil conductor. The unitis then placed in an oven and heated to cure the adhesive whichpermanently sets and firmly bonds the several turns of the apparatustogether to provide a rigid coherent unit.

The sectional view of FIG. 3, taken along line IIIHI of FIG. 1, is showngreatly exaggerated to illustrate the small area between each layer orturn of the apparatus where the liquid adhesive can flow. Like referencecharacters of FIG. 1 and FIG. 3 represent like parts of the The liquidadhesive is poured into the transformer coil at spaced intervals, forexample the four corners, and flows between the several layers of thecoil. The adhesive flows in an axial direction between the layers of thecoil to thereby coat a portion of each turn of the transformer with theliquid adhesive. The transformer coil is then heated to a temperaturesufiicient to cure the adhesive and thereby firmly bond each turn of thepaper and conductor to the adjacent turn to make a solid coherenttransformer coil able to withstand a complete electrical short circuitwithout damage due to mechanical stress and vibration.

A modified embodiment of this invention is shown in the sectional viewof FIG. 4. Like the coil of FIG. 2, a strip of thermally stabilizedinsulating paper is wound on a mandrel to form a coilform St}. A firstsection 82 of low voltage winding is wound on the coil form 80. Thefirst section 82 of low voltage winding is a plurality of turns ofinsulated wire, for example, an enameled rec tangular wire having acoating of an adhesive over the insulation. The coating of adhesive,such as an epoxy resin in the B stage, is non-tacky at ambienttemperature, but becomes soft and flows at elevated temperatures andpermanently sets when cool. A layer 84 of insulating paper is woundbetween the first section 82 of the low voltage winding and a secondsection 36 of the low voltage winding to provide additionallayer-to-layer insulation of 4 the low voltage winding. The next layeris a plurality of turns of the thermally stabilized insulating paperwound to form an insulating member 3%. The number of turns of insulatingpaper used to form insulating member 88 is determined by the voltagedifference between the low voltage winding and thehigh voltage winding.A duct 99 is formed on the ends of the coil by placing a corrugatedfibrous sheet or a plurality of wood or pressboard strips 91 at spacedintervals around the ends of the transformer between adjacent turns ofthe insulating member 88. The duct is provided for the circulation of aliquid dielectric adjacent to the low voltage winding.

The next layer 9% is the high voltage winding. The high voltage windingis made from a plurality of turns of a round or rectangular magnet wire92 having a coating of insulation thereon. The insulated wire has acoating of an adhesive material placed over the insulation. The adhesiveis, for example, an epoxy resin coating cured to its B stage prior towinding the wire onto the layer of insulation 88, that is, the adhesiveis non-tacky at ambient temperatures, but softens at elevatedtemperatures and permanently sets when cooled. The high voltage windinghas a turn of insulating paper between each layer of wire to providelayer-to-layer insulation of the coil. The paper is folded or cuffed atthe end to prevent axial motion of the wire. A final layer of insulation94 is wound on the high voltage winding from the thermally stabilizedinsulating paper.

After the entire transformer coil is wound it is removed from themandrel and a liquid adhesive, such as an epoxy resin, is poured betweenthe layers at spaced intervals around the coil so that it will flowbetween the layers of insulating paper. The transformer coil is heatedto cure the adhesive on the conductor and the adhesive between thelayers of the coil. The adhesive on the conductor when heated softensand flows slightiy, then when cooled permanently sets to therebypermanently bond the turns of the conductor together and also firmlybond the layers of the conductor to the layer-to-layer insulating paper.The adhesive poured into the layers of the coil when heated, thencooled, also permanently sets thereby bonding each layer of insulatingpaper to the adjacent layer of paper. This, of course, firmly bonds thelayers of insulating paper and conductors together to a rigid coherentunit able to Withstand a complete electrical short circuit withoutdamage to the transformer due to the vibration of the coil.

While there have been shown and described what are, at presentconsidered to be the preferred embodiments of the invention,modifications thereto will readily occur to those skilled in the art. Itis not desired, therefore, that the invention be limited to the specificarrangements shown and described and it is intended to cover in theappended claims all such modifications as fall within the true spiritandscope of the invention.

I claim as my invention:

1. A wound coil having a plurality of turns of insulating and conductingmaterial comprising, a first strip of insulating material wound toprovide a coil form, a first winding disposed on said coil form, asecond strip of insulating material disposed on said first Winding toform a tubular insulating member, a second winding disposed on saidtubular insulating member, and an adhesive disposed between the severalturns of said wound coil at spaced intervals around said coil, saidadhesive firmly bonding each turn of material to the adjacent turn ofmaterial at said spaced intervals.

2. A wound coil having a plurality of layers of insulatingand conductingmaterial comprising, a first tubular insulating member, a first windingdisposed on said first tubular insulating member, said first windingbeing formed from an insulated strip of metallic conductor, a secondtubular insulating member disposed on said first winding, a secondwinding disposed on second insulating member, said second winding beingformed from an insulated strip of metallic conductor, and an adhesivedisposed between the layers of said metallic conductor and insulatingmembers at spaced intervals around said wound coil, said adhesive firmlybonding the several layers together at said spaced intervals to form arigid coil.

3. A wound coil having a plurality of layers of insulating andconducting material comprising, a first strip of insulating materialwound to provide a coil form, a first winding disposed on said coilform, said first winding being formed from an insulated conductor havinga coating of adhesive over the insulation, a second strip of insulatingmaterial disposed on said first winding forming a tubular insulatingmember, a second winding disposed on said tubular insulating member,said second winding being formed from a conductor having a coating ofadhesive on top of a coating of insulating material, and an adhesivedisposed between said layers of insulating material at spaced intervalsaround said wound coil, said adhesive firmly bonding the several layersof insulating and conductors together at said spaced intervals 4. Awound coil having a plurality of layers of insulating and conductingmaterial comprising, a first strip of insulating material providing acoil form, a first winding disposed on said coil form, said firstWinding being formed from a first strip of metallic foil, a second stripof insulating material disposed on said first winding to form a tubularinsulating member thereon, a second winding wound on said tubularinsulating member, said second winding being formed from a second stripof metallic foil, and an adhesive disposed between the several layers ofinsulating material and metallic foil at spaced intervals around saidwound coil, said adhesive firmly bonding the layers of the coil togetherat said spaced intervals.

5. A wound coil for a transformer comprising, a first strip of thermallystabilized insulating paper providing a coil form, a first windingdisposed on said coil form, said first winding being formed from aninsulated conductor having a coating of adhesive thereon, a second stripof thermally stabilized insulating paper disposed on said first windingto form a tubular insulating member, a second winding disposed on saidtubular insulating member, said second winding being formed from aninsulated conductor having a coating of adhesive thereon and an epoxyresin adhesive disposed at spaced intervals around said wound coil, saidadhesive bonding said insulating paper and conductors together at saidspaced intervals to form a solid coherent coil.

References Cited in the file of this patent UNITED STATES PATENTS RabinsAug. 25, 1961

1. A WOUND COIL HAVING A PLURALITY OF TURNS OF INSULATING AND CONDUCTINGMATERIAL COMPRISING, A FIRST STRIP OF INSULATING MATERIAL WOUND TOPROVIDE A COIL FORM, A FIRST WINDING DISPOSED ON SAID COIL FORM, ASECOND STRIP OF INSULATING MATERIAL DISPOSED ON SAID FIRST WINDING TOFORM A TUBULAR INSULATING MEMBER, A SECOND WINDING DISPOSED ON SAIDTUBULAR INSULATING MEMBER, AND AN ADHESIVE DISPOSED BETWEEN THE SEVERALTURNS OF SAID WOUND COIL AT SPACED INTERVALS AROUND SAID COIL, SAIDADHESIVE FIRMLY BONDING EACH TURN OF MATERIAL TO THE ADJACENT TURN OFMATERIAL AT SAID SPACED INTERVALS.